In this work, the ferromagnetic resonance line width of a ferrite with two kinds of cations randomly distributed on a sublattice is calculated by taking into account the spatial fluctuation of both the spins and the exchange integrals. The uniform precession excited by the microwave field is scattered into degenerate spin waves by this inhomo-geneity. It is explained that the fluctuation of the pseudo-dipole forces considered by Clogston et al. was overestimated and is actually negligible in the present problem as comparing with the fluctuation of the exchange interactions. The result of our calculation not only gives rise to a large line width in the same order of magnitude as that observed with a number of inverted spinels, but also leads very naturally to an explanation of the noticeably small line width observed with the magnesium-manganese ferrite and the disordered lithium ferrite.
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